The present invention relates to a safety device for an accumulator, more particularly, it relates to a device wherein a sealing member which also acts as a temperature responsive sealing member such as packing is fixedly attached to a supply port communicating with a gas chamber, thereby the sealing member such as a fusible packing will melt upon such a temperature rise at the outer circumference as a fire so as to expel the gas in the gas chamber communicating with the supply port to the air outside and thereby prevent the accumulator from bursting due to the pressure rise caused by the expansion of the gas contained in the accumulator itself, and the supply port also displays functions which are originally required.
Heretofore, accumulators of this kind have been provided with, as shown in FIG. 13, at a supply port 1A of a pressure vessel 1, a recessed portion 2 and a gas passage 3, through which supply and discharge of gas are made to and from a gas chamber 4. The passage 3 is opened or closed by a counter sunk head bolt 5 screwed into the supply port from outside toward the inside, and the passage is sealed for the purpose of preventing the leakage of gas through the threaded portion 8, by fitting an O-ring 7 made of rubber or the like into a gap 6 defined between the lower slant face of the bolt 5 and the recessed portion 2.
In a conventional type accumulator, if the bolt 5 is loosened so as to release the gas in the gas chamber to check the gas pressure of the vessel, the O-ring 7 is urged upward by the gas escaping through the threaded portion 8 and is deformed. and further a part of the O-ring would protrude through a gap formed between the recessed portion 2 and the upper part of the bolt head and then would be torn off, therefore, there often occured gas leakage problems, unless the O-ring is replaced with a new one after each gas checking. In other words, the pressure vessel becomes unserviceable, unless replacement of the used O-ring and the filling of gas are done each time after the gas pressure checking has been made.
In addition, the accumulator of conventional type has a construction that it is not able to automatically discharge the gas in the vessel outside, even when the temperature at the outer circumference of the vessel should increase due to a fire or the like accompanying rise of gas pressure in the gas chamber.
That is, since the gap between the bolt 5 outside the O-ring 7 and the recessed portion 2 is set almost zero, it is impossible for the supply port to expel a large amount of gas within a short period of time, even if the O-ring has lost its sealing ability, thereby there is a possible fear that the accumulator in use may burst.